If you’re building an electrical circuit (series or parallel), chances are you’ll require a component called the resistor. Comes in a fixed or variable type, they are an important piece to your next circuit building project. Hence, today, we’ll aim to help you easily understand all you’ll need to know about this tiny electronic component!
In today’s tutorial on resistors, we’ll cover the following, giving you a deeper look into what exactly are resistors and how you can use them
- What is a resistor
- Resistor symbols and units
- Types of resistors
- How to read color bands on resistors
- Resistors in series circuit vs Resistors in parallel circuit
What is a resistor?
We know that a resistor is an electronic component but its functionality lies in resisting the flow of electricity, limiting the amount of electrons passing through a circuit.
Do note that resistors do not generate power, but instead consume power by relying on pairing with other components such as microcontrollers, and integrated circuits.
- You can draw inferences or analogies to a flowing water pipe, where a resistor is the is placed inside to reduce total water flowage.
Which Unit does a resistor use?
A resistor uses the unit Ohms (Ω) to measure electrical resistance. Established by Mr Ohm through Ohm’s Law in 1827, you can calculate resistance by simply taking voltage divided by current.
Calculating Ohms and which resistor should you use?
They are plenty of resistors ranging from 100 ohm, 200 ohm, 330 ohm, 470ohm, 10k, 4.7k, and so on. Hence, to understand which resistor is suitable for your circuit, you’ll need to calculate the resistance required.
- If you’re looking to purchase a kit that has all the resistors you’ll need, do consider our resistor kit above. It carries 500 resistors of 20 different values!
Here’s an illustration of how to go about picking a resistor that meets your project requirements:
- LED voltage: 20mA
- Converting it to Amps: 0.02A
- Power source: 5V
Resistor you should use: 5V / 0.02A = 250 Ω resistor. If you do not have a 250 resistor, it is best to use the next closest higher value to be safe!
How does a Resistor Symbol look like?
Like all electronic components, when a circuit is formed, you’ll use symbols for easier illustration. Based on the style that you more commonly see, a resistor symbol will look like either one below:
Understanding how resistor symbols look like would help you differentiate the different electrical components when analyzing a schematic circuit.
What are the types of Resistors
When it comes to resistors, there are mainly two types; Fixed and variable resistors. In this portion of the tutorial, we’ll explain both types and what it’s composed of.
Note: There are indeed still other types of resistors such as photoresistor that uses LDR sensor to detect resistance from light level changes and thermistor for temperature variations.
1. Fixed Resistors
By far the most common and widely used resistors on the market are the fixed resistors. They can either come in the form of through-hole or surface-mounted ones as seen above.
Through Hole Resistors
Among the two forms of fixed resistors, the long trim-able leads of the through hole resistors are more commonly integrated into breadboards or other prototyping boards. PCB, etc. The purpose for such integration tend to be for prototyping applications; with or without microcontroller boards connected.
As its name suggest, surface-mount resistors work differently compared to through-hole ones as it’s mounted on PCBs instead of connecting it into a electronic circuit, breadboard, etc. These surface-mount resistors are constructed in a tiny rectangular shape with conductive edges for functionality.
2. Variable Resistors
When talked about variable resistors, the three common forms comes to mind; Rheostat, Trimpot, and Potentiometer. The common features between these three are they are electrical components with fixed resistors integrated into it but provide variations for more complex applications (E.g. A slider on a potentiometer to provide a potential division of voltage, calculation of variable resistance, etc.)
What are the types of resistors composed of?
Now that we’ve understood the types of resistors, what are they made of? Here’s a quick breakdown of the three common resistor compositions!
|Carbon composition||Carbon composed resistors are the most common resistors in the past, but are seldom used now due to the newer compositions
The lack of temperature and proper heat management made it a poor choice nowadays as well.
Derived from mixing carbon granules with a binder.
|Metal-oxide composition||Metal-oxide film resistors are the most common option when using a resistor nowadays.
Compared to carbon, it has better temperature management, and lower noise level. making it a better option in terms of performance.
|Metal composition||Similarly to the above metal-oxide composition, metal film resistors provide comparable performance.
As its name suggest, it uses a metal film instead.
Commonly used when leaded resistors are required.
Resistor color code, bands, and How to read them?
Picked out a resistor and find out that it doesn’t have a marking of its value on it? Yes, for resistors, instead of displaying its outright value, it’s marked with color bands for you to decode!
Decoding a resistor color band with example
Step 1: Determine whether your resistor is a four, five, or six band resistors.
Band refers to the number of color markings on your resistors.
- Four bands: First two color markings are resistor’s value, third band is the multiplier value, and the fourth band is the tolerance value
- Five bands: First three color markings are resistors’ value, fourth band is the multiplier value, and the last band is the tolerance value
- Six bands: Additional band for color coefficient
Step 2: Refer to the color code table to find the value of your resistor
Based on the 4-band resistor example on the table, here’s how to derive the value 560k:
- First color band is green, table value: 5
- Second color band is blue, table value: 6
- Value after first and second color band: 56
- Third color is yellow, table value (multiplier): 10KΩ
- 56 x 10KΩ = 560 KΩ
- Fourth color is brown, indicating the tolerance (how much more/less can the actual resistance of the resistor can be used for): ±5%
The value of resistor: 560k Ω with ±5% tolerance
Lazy to refer to the color table and want a free tool to help you calculate your resistor value?
Use this free tool to determine the information for color banded resistors. All you need is to select the no. of bands of your resistor and its respective color. The resistor color code calculator will then calculate the value for you!
Resistors in Series and Parallel Circuits
We’ve talked about calculating resistance in the earlier part of today’s tutorial but what if you pair multiple resistors together in a series or parallel circuit? How can you calculate total resistance then?
Calculating resistance in a series circuit
Here we have three resistors in a simple series circuit. All you’ll have to do to calculate total resistance is to take R1 + R2 + R3! That simple!
Calculating resistance in a parallel circuit
Finding the total resistance value in a parallel circuit is not as simple as a series circuit. However, if you follow the formula below, it wouldn’t be that difficult!
- Total resistance = 1/R1 + 1/R2 + 1/R3
- If you only have two resistors of equal values, total resistance = half of resistor value
Do note that for a parallel circuit, if you were to continue adding resistors, total resistance will drop due to its inverse relationship.
That’s all for today on resistors. I hope with today’s blog, you get a deeper understanding of what is a resistor, how it works and calculating total resistance!
- For more information on color coding, bands, do refer to this post
With resistors being such an essential component to every electronic circuits, you’ll bound to require one for your next circuit building project! Hence, to ensure you are well covered with the required resistors, do consider our resistor kit!